The present invention relates to positioner devices and, more specifically, to such devices for determining and maintaining or holding a specific position or target such as may be needed in orthopaedic surgery for the placement of locking.
Bone fractures, such as long bone fractures of the upper and lower extremities, may be stabilized with metal rods or so-called intramedullary nails that are implanted into the hollow center or so-called intramedullary canal of these bones. However, an implanted intramedullary nail may provide only limited stability to a fractured bone. That is, the two ends of the fractured bone may rotate, angulate and/or telescope on the implanted nail.
The intramedullary nails may achieve greater stability by the use of locking screws that may pass through the bone and the intramedullary nail. Such locking screws may be placed at opposite ends of the implanted intramedullary nail and may lock the parts or sides of the fractured bone to the implanted intramedullary nail. As a result, the locking screws may prevent the fractured bone from rotating, angulating and/or distracting upon the implanted intramedullary nail.
The region of the bone where the nail is implanted is identified as proximal and the opposite end of the intramedullary nail is distal. Intramedullary nails have two proximal and two distal screw holes. The locking screws should be placed precisely through both the bone and screw holes in the implanted intramedullary nail. Placement of the proximal transverse locking screws, near to the insertion point of the intramedullary nails may be relatively simple. However, placement of the two transverse locking screws across both the bone and distal end of the intramedullary nail may be relatively difficult.
A number of steps may be undertaken to successfully place locking screws across both a fractured bone and an implanted intramedullary nail. First, X-rays or the like may be used to locate the screw holes in the intramedullary nail. Second, screw holes may be drilled through the bone on either side of each screw hole. Third, the length of the locking screw needed to pass through both the bone and the intramedullary nail may be determined by passing a depth gauge or the like through the drilled holes and intramedullary nail. Fourth, the selected locking screw or screws are implanted, transfixing the bone and the intramedullary nail.
The above-described steps for placement of the proximal locking screws may be readily accomplished with a proximal based outrigger bushing that is attached to the proximal end of the implanted nail. Such outrigger bushing may provide rigid concentric alignment with the proximal screw holes so as to enable rapid and reliable drilling, measurement, and placement of the proximal screws. On the other hand, an outrigger bushing with a proximal origin for the distal screw holes may not perform satisfactorily due to the mechanical stress on the outrigger and/or the unpredictable distortion of the distal end of the intramedullary nail during implantation.
Distortion of the distal end of an intramedullary nail may occur as it is implanted into a bone. That is, the distal end of the nail may rotate, angulate and/or deflect within the intramedullary canal of the bone. Accordingly, a fixed proximal based outrigger bushing may not compensate for the actual position of the distal screw holes and may not function adequately.
An adjustable-type outrigger bushing may compensate for the distortion of the distal end of an implanted intramedullary nail. However, such adjustable-type outrigger bushing may require excessive tinkering to obtain correct alignment with the screw holes in the implanted nail. This tinkering may necessitate an increased use of X-rays and as such may increase undesirable X-ray exposure to the surgeon, patient and operating room staff, and may also lengthen the surgical procedure.
Outrigger bushings with a proximal origin for the distal screws may effectively have a long lever arm. Uncontrollable micromotion of such long lever arm may prevent the successful use of these devices. Even when an outrigger bushing, such as the adjustable-type outrigger bushing is eventually aligned with the distal screw holes, the alignment may not be sustained due to micromotion.
The combined mechanical difficulties of the proximal based outrigger and the distortion of the implanted nail have thwarted the successful development of a proximal based outrigger bushings for the distal screw holes.
To place distal locking screws in an implanted interlocking nail the location of the distal screw holes should be known. However, the distal end of the nail may be hidden from view within the intramedullary canal of the bone and visualization of the distal screw holes may require X-ray guidance provided by a portable adjustable X-ray machine or the like in the operating room. Such X-ray machine may be manipulated to a position in which the path of the x-ray beam is parallel with the long axis between a single set of screw holes in the intramedullary nail. When this alignment is accomplished, the X-ray appearance of the screw holes may be substantially perfect circles. The X-ray machine may be maintained in axial alignment with a distal screw hole throughout the previously-described second through fourth steps for placement of a distal interlocking screw.
The lack of success of proximal origin outrigger bushings for the distal locking screws has stimulated the development of a number of devices and techniques to accomplish the placement of these screws. However, although these devices may locate the distal screw holes and facilitate the drilling of holes in bone, these devices may not provide guidance which may be needed for the steps of measuring the length of the locking screw and/or placing the locking screw across the bone and intramedullary nail. The steps of measuring the optimum length of the locking screw and placing the selected screw may be very difficult to achieve. The successful drilling of a screw hole across the bone and intramedullary nail may not facilitate the necessary and technically difficult steps of measuring or implanting the locking screw.
There is a substantial amount of empty space concentrically surrounding the implanted intramedullary nail. The drilled screw hole in the bone may not be of sufficient length or thickness to serve as a bushing to align the depth gauge or locking screw with the screw hole in the interlocking nail. The depth gauge and locking screw will frequently miss the screw hole and deflect off the intramedullary nail. Therefore, measuring the length of the locking screw and the implantation of the measured locking screw may necessitate the use of additional X-rays and, as such, may result in excessive x-ray exposure to the surgeons, patient and/or operative team and may substantially lengthen the surgical procedure regardless of whether the drilling of the screw hole(s) across the bone and intramedullary nail was successful.